This invention relates to producing a uniform magnetic field or the shielding or cancelling a magnetic field produced by the use of superconductive passive rings positioned perpendicular to the electromagnet coil magnetic field between the coil and the resulting conditioned magnetic field. The size of, quantity of, and the material of construction of the superconductive passive rings determine the resulting conditioned field.
It has long been known that a high uniformity magnet field is required in many applications such as plasma separation and particle accelerators. Considering the allowable degrees of design freedom, a desirable high uniformity cannot be achieved by design alone. Correction or compensation coils are required to accomplish the high degree of uniformity required for these certain and other applications. Generally active compensation coils are used comprising a separate winding which is charged to the desired current distribution to promote high uniform density. In this appication active compensation coils are positioned between the source of the principle magnetic field and the resulting conditional or uniform field, i.e. around the inside of a cylindrical bipolar magnet or around the outside surface thereof. In this application the active coils are sized ad energized to establish a magnet field which passes and distributes a highly uniform magnetic field from the principal field external of the active compensation coils.
Shielding is established by increasing the field created by the active compensation coils to a degree that these fields are sufficient to neutralize the principal magnetic field exterior of the active compensation coils.
An example of active compensation coils for the neutralizing (shielding) the principal magnetic field can be found in U.S. Pat. No. 3,671,902 by William F. Westendorp and assigned to the General Electric Company and U.S. Pat. No. 4,032,959 by Roger W. Boom et al. and assigned to Wisconsin Alumni Research Foundation.
Although no specific prior art directed to establishing highly uniform fields by use of active magnetic coils was found in a search of the prior art, it is believed that, this type of magnetic field conditioning does exist in the art, and a uniform field would be produced by reducing the current used for shielding in the active compensating coils to a degree of intensity less than that required to neutralize the magnet effect of the principal field.
There is a continuing need especially in high magnetic field applications to establish high uniformity and shielding.